Fuel cells that operate in conjunction with replaceable fuel canisters or cartridges filled with, for example, gaseous hydrogen, methanol, butane or diesel fuel, are a developing technology. These types of fuel cells are designed to compete with the various battery solutions that power consumer products. The competitiveness of these fuel cells with regard to batteries depends on a number of factors, such as the energy density of the fuel in the canister; the ability of the fuel cell to convert chemical energy to electrical energy with certain efficiencies; and the need to keep the fuel cell stack, along with associated fluid pumping and power control components, no larger than that of a competitive battery.
One possible use of portable fuel cell systems is to recharge batteries while the consumer is engaged in various other activities. Any time batteries are being recharged there is an elevated risk that the battery will fail catastrophically in a variety of ways, including possible fire. This catastrophic failure is very rare, and the risk it poses is generally considered acceptable in most situations where batteries are currently plugged into the wall. The availability of a portable fuel cell system potentially allows this risk to be present in environments where battery charging has not historically been possible. For example, unattended charging in a suitcase on an airplane is now technologically possible.
In some safety critical environments, it is desirable to have a portable fuel cell system which is of a type that will not charge batteries when an attached portable electronic device is not in use. This standard is currently a requirement in the United States of America for fuel cell systems used on commercial aircraft as specified in the Code of Federal Regulations 49 C.F.R. §175.10(a)(19)(ix).